Not Applicable
The present invention relates generally to joints, and more specifically to flexural joints used in semiconductor processing machines.
Major objectives in the design of semiconductor processing machines include high throughput, low cost, small footprint, and high yield. Achievement of these objectives results in improved return-on-investment (ROI) for the end-user and increased profit and sales for the manufacturer. As demand increases for faster semiconductor devices, semiconductor-processing machines have increasingly required components which are vacuum compatible, non out-gassing, having low or no wear, and having low or no stray magnetic flux. The sum of a machine""s performance is a function of its components. One of many types of machine components is a joint.
Joints can be used to maintain a distance between two moving parts of a machine. The maintained distance can be in any combination of six directions (three translational and three rotational). Joints need to be stiff in the directions in which the distance is to be maintained and compliant in the directions in which the distance will vary. Typically, joints require adequate stiffness to minimize vibration amplification between machine components, minimizing positional errors. Additionally, adequate stiffness allows for faster positioning control in the compliant directions. Typically, joints require adequate compliance to minimize the force required to move the parts in the compliant directions. A well-designed joint can improve a machine""s performance by increasing throughput, lowering positioning errors, increasing reliability, and by reducing overall machine size and weight.
There is a need, in the design of particular semiconductor processing machines, for a joint having the freedom to move in three directions: z (up-and-down), "THgr"x (rotation about the x-axis), and "THgr"y (rotation about the y-axis). At the same time, such a joint should have high stiffness in the x, y, and "THgr"z directions. Additionally, such a joint should have the following characteristics: non out-gassing, not have stray magnetic flux, no wear nor particulate generation, low or no friction, no xe2x80x9cloosenessxe2x80x9d or xe2x80x9cbacklash,xe2x80x9d long life, low or no heat transfer to connected elements, be relatively compact, and be relatively low in cost.
Many conventional joints cannot meet the above requirements. Journal bearing joints have wear and create particles. Ball and roller bearing joints also wear and create particles. Fluid bearings are difficult to seal in a vacuum environment and require pumping and filtration support equipment. Magnetic bearing joints have stray magnetic flux, are large, and require heat removal systems. Therefore, given the above requirements, the best type of joint to use is a flexural joint.
Flexural joints offer the key advantages of: non out-gassing, no stray magnetic flux, no wear nor particulate generation, low or no friction, no xe2x80x9cloosenessxe2x80x9d or xe2x80x9cbacklash,xe2x80x9d long life, low or no heat transfer to connected elements, relative compactness, and relatively low cost. Although flexural joints have been used for various application, there exists a need, in the design of particular semiconductor processing machines, for a flexural joint which is compact, relatively free in the z, "THgr"x and "THgr"y directions, and relatively constrained in the x, y, and "THgr"z directions.
The flexural joint of the present invention includes a translational joint, a first support member, a first rotational joint, and a second rotational joint. The translational joint allows a first component and a second component to be moved with respect to each other along the z-axis. The translational joint includes a first translational flexural member that connects a first rigid member and a base rigid member. The first support member is attached to the base rigid member. The first rotational joint allows the first component and the second component to be moved with respect to each other in the "THgr"x direction. The first rotational joint includes a first rotational flexural member that is attached to the first rigid member. The second rotational joint allows the first component and second component to be moved with respect to each other in the "THgr"y direction, wherein the second rotational joint includes a second rotational flexural member that is attached to the first support member. The three-degree of freedom joint substantially prevents the first and second components from moving with respect to each other in the x, y, and "THgr"z directions. Therefore, the flexural joint allows for minimal vibration amplification between the connected components, smaller positional errors, and faster positioning control in the compliant directions. Throughout this disclosure, the flexural joint of the present invention may be referred to as the xe2x80x9cthree degree of freedom jointxe2x80x9d since it moves in three degrees of motion.
These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and the accompanying figures, which illustrate by way of example the principles of the invention.